The 33-year-old Fashion Star alum has worked hard to get to this point. As she reveals in an interview with USA Today, she "jumped back on Weight Watchers" as soon as she got the all-clear from her doctor, and has been exercising regularly ever since, often with fiance Eric Johnson.

"I saw the results really quickly," she tells the paper of her success on Weight Watchers' "Simple Start" plan and "PointsPlus" plan. It helps, of course, that she has "somebody who comes in and helps out" with the food preparation. "I do want to make sure I stick with the right recipes, and obviously my schedule is a little jam-packed," she explains.

Besides that, the designer says, she's just "an okay cook" -- definitely "not one of the best." Her husband-to-be, though, is "really good at chopping vegetables," something she herself has not yet mastered.

One thing she has gotten very good at? Fitting exercise into her daily routine. "With both kids, I'm running up and down my stairs a million times," she tells USA Today of son Ace, almost 6 months, and daughter Maxwell, 19 months. "Kids can keep your metabolism going."

She's also been working out with celeb trainer Harley Pasternak four days a week for 45 minutes. And she and Johnson take long walks together, too. "I try and walk about four miles a day consistently," she says. "It makes me feel better...Working out and being active overall makes me a happier person to be around."

Losing weight isn't her only endgame, though. Her real goal? "To be the best version of myself and to feel great," she says. "I want to be a great mom and a great example to my kids."

That means not just living a healthy lifestyle but also rising above the critics and weight bullies. "It does get old having people harping on how much you weigh or your body after pregnancy," she confesses. "I need to feel comfortable in my own skin. People are going to pick me apart no matter what I do."

Besides that, Simpson has more important things to worry about -- like her upcoming wedding to Johnson and designing her gown. "I've been pulling all kinds of sketches for dresses and colors," she says. "It's a good goal for me. It's good for me to feel the best I've ever felt when I walk down the aisle."

No doubt Johnson will take care of at least part of that. "I'm the luckiest girl in the world to have Eric with me and by my side," she gushes, noting that they have their hands full with two kids under the age of 2. "He's an unbelievable dad."